Category Archives: daily chores

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Compress PDFs and combine in Linux

Wanted to reduce the size and also combine a few scanned files in pdf format.

Ghost script was very nifty

gs -dBATCH -dNOPAUSE -q -sDEVICE=pdfwrite -dPDFSETTINGS=/ebook -sOutputFile=out.pdf scan1.pdf scan2.pdf scan3.pdf scan4.pdf

-dPDFSETTINGS=/ebook – was the key for resolution

-dPDFSETTINGS=/screen   (screen-view-only quality, 72 dpi images)
-dPDFSETTINGS=/ebook    (low quality, 150 dpi images)
-dPDFSETTINGS=/printer  (high quality, 300 dpi images)
-dPDFSETTINGS=/prepress (high quality, color preserving, 300 dpi imgs)
-dPDFSETTINGS=/default  (almost identical to /screen)


Refer : http://milan.kupcevic.net/ghostscript-ps-pdf/#refs

Thanks to http://stackoverflow.com/questions/8158584/ghostscript-to-merge-pdfs-compresses-the-result
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Server push with node.js and socket.io

Continuing my exploration on Node.js – I started working on the server push. I had read that socket.io (a node.js module).

Since I had node installed in my Ubuntu 12.10 (64-bit) – I was able to get the basic example done in 5 minutes.

1. Create a directory serverpush and go into that directory

sai@sai-home:~$ mkdir serverpush
sai@sai-home:~$ cd serverpush/

2. Create a package.json in the serverpush directory

{
“name”: “serverpush”,
“version”: “0.0.1”,
“private”: true,
“scripts”: {
“start”: “node app”
},
“dependencies”: {
“socket.io”: “~0.9.6”
},
“engines”: {
“node”: “0.8.x”
}
}

3. To install all dependancies – we need to use npm (node package manager) that uses the information in package.json

sai@sai-home:~/serverpush$ npm install -d

The above command installed all missing dependencies

4.Next is to create the node.js server file called app.js

var app = require(‘http’).createServer(handler)
, io = require(‘socket.io’).listen(app)
, fs = require(‘fs’)

app.listen(8888);

function handler (req, res) {
fs.readFile(__dirname + ‘/index.html’,
function (err, data) {
if (err) {
res.writeHead(500);
return res.end(‘Error loading index.html’);
}

    res.writeHead(200);
res.end(data);
});
}
function sendData(socket){
var thisRef = this;
var currentTimeObj = new Date();

// though there are better ways to format time – living with this for the time being
var formattedTime = currentTimeObj.getDate() + “-” +currentTimeObj.getMonth() + “-” + currentTimeObj.getFullYear() + ” ” + currentTimeObj.getHours() + “:” + currentTimeObj.getMinutes() + “:” + currentTimeObj.getSeconds();
socket.emit(‘timeUpdate’, { currentTime:  formattedTime});
setTimeout(function(){
sendData.call(thisRef,socket)
},1000);
}

io.sockets.on(‘connection’, function (socket) {
socket.emit(‘welcomeMessage’, { welcome: ‘Welcome to server poller’ });
sendData(socket);
});

4. Create the index.html that will be used as the client code

<!DOCTYPE html>
<html>
<head>
<title>Server Time poller</title>
<meta charset=”UTF-8″>
</head>
<body>
<div id=”statusMessageDiv”>

</div>
<div id=”serverTimeDiv”></div>
</body>
<script src=”https://ajax.googleapis.com/ajax/libs/jquery/1.8.2/jquery.min.js”></script&gt;
<script src=”/socket.io/socket.io.js”></script>
<script>
$(document).ready(function(){
var socket = io.connect(‘http://localhost&#8217;);
socket.on(‘welcomeMessage’,function(data){
$(“#statusMessageDiv”).html(data.welcomeMessage);
});
socket.on(‘timeUpdate’, function (data) {
$(“#serverTimeDiv”).html(data.currentTime);

});
});
</script>
</html>

5. Run the server file using node

sai@sai-home:~/serverpush$ node app.js
info  – socket.io started

6. Launch the server through browser http://localhost:8888 – we will see our server time running

That’s it  – really amazed at the productivity with Node.js

Planning to use server push to write a twitter clone next 🙂